Thread-grinding machine



A. E. LARSSON THREAD GRINDING MACHINE July 15. 1924.

Filed March 16, 1918 6 Sheets-Shea?l l Amm E. Lamm Br moe/vn A. E. LARSSON THREAD GRINDING MACHINE Jguly 15 1.924.`

Filed March x16 1918 v6 Sheets-Sheet 2 mm .Q @am Q l/WETOH July 15 1924. 1,501,544

A. E. Il ARSSON THREAD GRINDING MACHINE med March 16, 1918 e sheets-'sheet 5 A omver July 15 1924. 1,501,544

A. E. LARSSON THREAD GRINDING MACHINE Filed March 16 1918 6 Sheets-Sheet 4 A amv/Er July 15 1924.

A. E. LARSSON THREAD GRINDING MACHINE Filed March 1e INVENTOH rra/MEV Em .Hrm

MME-1mm er ,j

July 15., 1924. 1,501,544

A. E. LARSSON l THREAD'GRINDING MACHINE Y Filed March 16, 1918 6 Sheets-Sheet 6 B' J. In@

jgO/WEY i Paieniedauly 15,1924.

COMPANY, F NEW YORK, N. Y., A CORPQRATIGN 0F NEW JERSEY.

- THREAD-GRINDING MACHINE Application filed March 16, 1918. Serial No. 222,928.

To all whom it may concern:

Be it known that I, ANDERS E. LAIgssoN, a citizen of the United States, residing at Hartford, in the county of Hartford and State of Connecticut, have invented certain new and useful Improvements in Thread- 'Grinding Machines, of which the following is a specification.

The principal object of the invention is to provide a machine which is adapted to accurately and rapidl grind the threads on thread gages and ot er threaded objects. In accordance with the invention, relative longitudinal movement is effected between 16 the Wheel and the blank being groundA in timed relation with the rotation of Athe blank. The rotation of the blank and the relative longitudinal movement are periodically reversed. The wheel is maintained in engagement with the blank during movement in one direction and is disengaged during movement in the other directlon. The relative vlongitudinal movements, accompanied by the engagement and disengagement of the wheel, are continued until the grinding is completed. The Wheel can be fed toward the blank at each engagement therewith, this feeding preferably being effected automatically. Another object of the invention is to rovide improved structural features for e ecting the operations above set forth.

A further object of the invention is to provide improved means whereby the cycle of operations ca'n be modified to adapt the machine for the grinding of either righthand threads or left-hand threads as reuired. Still another object of the invention is to provide, in combination with the other parts of the machine, improved means for accurately and easily dressing the` grinding wheel and maintaining the shape thereof.

Additional objects of the invention will be apparent from the following specification and claims.

In the accompanying drawings I have shown one embodiment of the invention, but it willbe understood that the drawings are merely for the purpose of illustration and are not to be construed as defining or limiting the scope of thevinvention, the accompanying claims being relied upon for that purpose.

Of the drawings:` Fig. 1 is a front elevation. Fig. 2 is a plan view.

- PATENT! OFFICE.. i

v .ANDERS n massen, orl Hammam coNNEcTIcUT, .Ass'ronoa To PRATT a WHITNEY i Fig. 3 is a detail view showing-the con- Y nection between the face plate andthe spindle. l

Fig. 4 is a left endelevation.` Fig. 5 is a fragmentary view similar to Fig. 4 but showing the change-speed gearing in position for cutting Aleft-hand threads.

Fig. 6 is'a fragmentary vertical sectional vievvtaken along the lines 6-6 ofFigs.l 4 an Fig. 7 is a vertical sectional'view taken along the line 7-7 of Fig. 6.

Fig. 8 is a vertical sectional view taken along the lines 8-8 of Figs. 1 and 6. Fig. 9 is a vertical sectional view taken along the line 9--9 of Fig. 6.

Fig. l0 is a fragmentary sectional View taken along the line 10-10 of Fig. 8.

Fig. 11 is a fra entary view taken fromthe right, partly 1n elevation and partly in section along the line 11-11 of Fig. 1.

Fi 12 is a fr a entary front viewl showing t e feed mec anism.

Fig. 13 is a fragmentary sectional view I taken along` the line 13-13 of Fig. 12.

Fig. 14 is a fra entary planview on an enlarged scale s owing the wheel dressing mechanism. i

Fi 15 is a front view, partly in section, I

showing the parts appearing in Fig. 14.

Referring to the drawings, 1 represents the main frame of the machine upon which all the other parts are supported. Carried by the frame is a table 4, and preferably' the table is longitudinally .movable along two horizontal guideways 2 and 3 formed onthe top of the frame.

Carried by the table 4 "is alheadstock 5- having a center 6 and a tailstock 7 having a center 8. The center 6 of the headstock is carried by a rotatable spindle 9 mounted in suitable bearings 10,11 and 12. For rotating the spindle 9 there is provided. a

belt pulley 13. This pulley may. be directly connected withl the spindle but, by prefer-` ence, provision ismade4 whereby it.l may be connected indirectly to the spindle, asy for instance by means ofsuitable back gearing' such as indicated at 13a.

The mista-,k- 7 is adjustable-longitudinal;

ly of the table and is adapted to be held in adjusted position by means of a T-bolt 14 entering a longitudinal T-slot in the table, as shown in Fig. 11.- For tightening the bolt 14 a handle 15 is provided. The center 8 is carried by a sleeve 16 which is movable longitudinally of the tailstock by means of ahand wheel 17. The sleeve 16 can be clamped in adjusted position by means of a screw controlled by a handle 18. Preferably the part of the tailstoc-k frame which serves as a bearing for the sleeve 16 is connected with the vlower part of the tailstock frame by anarrow neck portion 19 which is ada ted to yield or spring under pressure. xtending horizontally from the bearing portion' 1s an integral arm 2O having a Vertical aperture through which extends a bolt 21. This bolt Ais connected at its lower end to the base of the tailstock and carries knurled nuts 22 and 23 by means of which the arm 20 can be slightly raised or lowered. The arm 20 is provided with an aperture through which` extends the bolt 14 and a sleeve or bushing thereon. B means of the arm 2O and the nuts 22 an 23 the bearing portion of the tailstock together with the sleeve 16 and the center S can be moved slightly forward or rearward, the neck portion at 19 springing to permit such movenient, This construction makes it possible for the tailstock center 8 to be accurately alined with the headstock center 6 without the use of a transverse slide such as has heretofore been deemed necessary.

In the drawings I have illustrated an internal thread gage in\ process of being ground, but it will be understood that a machine embodying. t-he invention is not limited for use in grinding such gages. As illustrated, the gage is indicated at A, being held between the two centers 6 and 8 in the usual manner. The gage carries a dog 24 which is engaged by a face plate 25 carried by the spindle 9. n this way rotation is transmitted from the spindle to the gage. Preferably the face place 25 is angularly adjustable with respect to the spindle and, as illustrated in Fig. 3, the face plate is provided with arcuate T-slots in which are situated the heads of T-bolts 26. 26. These bolts extend through a tiange 27 secured to the spindle. When the boltsare loosened the face plate, together with the dog and the gage, can be adjusted angularly with respect to the spindle, and when the boltsA are tightened the face plate, together with the dog andthe gage, are locked in adjusted positions. The purpose of this adjustment will more fully appear later.

At 28 I have shown the wheel for grinding the thread convolutions on the gage A. Themechanism for rotating the wheel and for effecting the necessary adjustments thereof will be fully described later7 but for the present it is sutlcient to state that the wheel is so mounted that relative longitudinal movement may be effected between it and the blank being ground. Preferably, as already stated, the table 4 and the blank are longitudinally movable and in this case the wheel is fixed against bodily movement during the grinding operation.

The carriage 4 is moved longitudinally in timed relation to the rotation of the spindle, and any suitable mechanism may be used for this purpose. Preferably I provide a lead screw 29 which is secured to the carriage for longitudinal move-ment therewith. The lead screw extends through a threaded aperture in a fixed boss 30 projecting upward from the main frame. Suitable gearing is provided for connecting the lead screw 29 with the spindle 9. As illustrated, a pinion 31 is secured to the outer endof the spindle and a gear 32 is secured to the outer end of the lead screw. An armv 33 is mounted for movement about t-he axis of the lead screw and this arm may be clamped in adjusted positionby means of a screw 34. The arm 33 is provided with two parallel longitudinal slots in one of which is positioned a bearing stud 35. Rotatably mounted on the bearing stud 35 is a gear 36 meshing with the pinion 31. Also rotatably mounted on the stud 35 and -connected with the gear 36 is a second smaller gear 37. The gear 37 meshes with the aforesaid gear 32 on the lead screw. It will be see-n that by meansof this gearing the lead srew is turned simultaneously with the spindle and at a definitely related speed. By removing some of the gears and substituting others of different diameters. the speed ratio may be changed as desired. In practice the proper gears are selected to cause the lead screw to move the carriage, during each revolution of the spindle, a distance equal to the pitch of the threads to be ground on the gage A.

During grinding the spindle is rotated in the direction indicated by the arrow in Fig. 1 and therefore for grinding right-hand threads it is necessary for the table and the parts carried thereby to be moved toward the right during grinding. The gearing described will effect movement in the proper direction toward the right. For grinding left-hand threads, however, it is necessary for the carriage movement to be reversed, and for this purpose a bearing stud 38 is mounted in the other slot of the arm 33, as shown in Fig. 5. The stud 35 is adjusted outward and an yidler gear 39 is placed on the stud to mesh with the gear 37 and also with the gear 32. This reverses the direction of rotation of the lead screw and therefore the direction of movement of the table.

At the end of the table movement toward the right, the table movement must be reversed to return the blank to the proper position for a subsequent grinding action of the wheel. Inasmuch as the Wheel must be passed over the blank several times to complete the grinding operation, it is. necessary to reverse the spindle rotation and thus reverse the table movement at regular intervals. For this purpose the driving and reveising mechanism now to be described is provided.

Secured to the main frame at the rear is a gear box or casing 40. Horizontally mounted in the casing is a rotatable shaft 41, The shaft projects from the casing toward the left, as viewed in Figs. 1 and 2, and carries a wide belt pulley'or drum 42. A belt 43 passes over and around the drum 42 and the pulley 13 on the spindle 9. It will be seen that when the shaft 41 is rotated the Spindle 9 will be similarly rotated. The drum 42 is of suflicient width to permit the pulley 13 to be moved longitudinally with the table without interfering with the power connection.

The machine is provided at the extreme rear with a horizontal main drive shaft 44. This may be driven in any usual or preferred manner, as for instance, by means of a belt 45 passing over a pulley 46 secured to the shaft. The shaft 44 carries at its lefthand end a pulley 47 which is in register with a pulley 48 secured to a horizontal shaft 49. The shaft 49 is mounted in a bearing in the casing 40 and is adjacent and parallel to the shaft 41. A belt 50 connects the two pulleys 47 and 48, thus continuously rotating the shaft 49 so long as the main drive shaft 44 is rotated.

Gearing is mounted within the casing 40 forr transmitting power from the shaft 49 to rotate the shaft 41 in either direction, preferably more rapidly in one direction than in the other. As illustrated in Figs. 6 and 7, the shaft 49 carries a pinion 51 which meshes with a gear 51 loosely mounted on the shaft 41. The gear 51 meshes with a gear 52 on a shaft 53 which is parallel to the shafts 41 and 49. The shaft 53 carries at its opposite end a pinion 54. An arm 55 is mounted for movement about the axis of the shaft 53 and has a longitudinal slot in which is secured a bearing stud 55a. Mounted on the stud 55a is a gear56 which meshes with the pinion 54. Also mounted on the stud 55a is a pinion 57 which meshes with a gear 58 loosely mounted on the shaft 41. Splined to the shaft 41 between the gears 51 and 58 is an annularly grooved clutch collar 59 having at its ends teeth adapted to mesh respectively with teeth formed on the gear 51aL and on the gear 58. When the clutch collar 59 is in its righthand position, as viewed in Fig. 6, the drum 42will be rotated slowly in the direction indicated by the arrow, thus rotating thel spindle in the proper direction for grinding. The speed of rotation may be changed by removing one or more of the gears 54, 56 and 57, and substituting others of different diameters. When the clutch collar 59`is in its left-hand posltion, the drum 42 will be rotated in the other direction at a much higher speed, thus reversing the direction of rotation of the spindle.

For automatically shifting the clutch collar 59 to effect reversal, the following mechanlsm 1s preferably provided. A forked lever 60 is horizontally pivoted in the casmg at 61, and this lever is provided with shoes which enter the groove in the collar 59. The lever'is provided with a pointed projection 62 which cooperates with a spring-pressed pointed plunger 63. The plunger serves to hold the lever in one or the. other of its extreme positions, thus malntaining the clutch collar in engagement with the gear 58 or in engagement with the gear 51. carries a roller 64 which is adapted to be engaged by a double cam 65 loosely mounted on the shaft 53. Connected with the cam is a flange 66 on which is pivotally mounted a latch 67 adapted to engage a toothed wheel 68 secured to the shaft 53. The latch 67 is providedwith a spring which tends to move it int-o engagement with the toothed wheel. When the latch is so engaged, the flange 66, together with the cam 65, is caused to partake of the rotary movement of the shaft 53. Pivotallyv mounted within the outlines of the main frame, as illustrated in Fig. 8, are two levers 69 and 7 0 carrying respectively attheir rear ends trips 71 and The upper end` of the lever 6()` 72. These trips are adapted to contact with the tail of the latch 67 as it is bodily moved and to thus disengage the latch from the toothed wheel 68. Stops 73 are provided for limiting the inward movements of the lever ends carrying the trips 71 and 72. One of the levers, as for instance 69, carries a spring-pressed plunger 74 which bears against the other lever and thus tends to move both of the levers in the direction to swing the trips 71 and 72 inward. As illustratcd, the latch 67 is in contact with the trip 71 and is thus held disengaged from the toothed wheel 68. The flange 66 and the cam 65 are thus held idle. If the lever 69 be swung in the counterclockwise direction the trip 71 will be disengaged from the latch 67 which will immediately engage the toothed wheel 68 and thus rotate the flange is then moved in the clockwise direction,

the latch 67 will be again released and the flange and the cam will be again rotated until the latch 67 returns to the position shown, whereupon the rotation will be again stopped.` Preferably, for assisting in holding theiange and the cam in their idle positions, there is provided a spring-pressed plunger 75 which is adapted to enter notches 76 and77 in the flange 66. Each notch has one side beveled so that the plunger will be forced out when the flange is rotated.

.As shown in Figs. 6 and 10, the cam 65 is so Ishaped that, during the movement of the latch 67 from the trip 71 to the trip 72, the lever 60 will be swung in the clockwise direction. This connects the direct high speed drive: and the drum 42 is rotated in the direction opposite to the arrow in Fig. 6. When the latch 67 moves from the trip 72 to the trip 71, the lever 60 is swung in the counter-clockwise direction, thus connecting the indirect low speed drive which rotates the drum 42 in the direction of the arrow in Fig. 6. The two sides of the cam are far enough apart to permit the roller to be maintained in a central neutral position by means to be presently described.

Mounted in suit-able bearings at the front of the machine is a vertically slidable rod 78 carrying collars 79 and 80 which respectively engage the upper surface of the lever 69 and the lower surface of the lever 70. A lever 81 is horizontally pivoted between its ends to the front of the machine and is connected at one end to the upper end of the rod 78. The other end of the lever is connected with the lower end of a link 82. The upper end of the link 82 is adapted to be connected with one or the other of two arms of a three-armed bell-crank 83 which is horizontally pivoted to the main frame. The third arm of the bell-crank 83 extends upward and is adapted to be engaged successively by two dogs 84 and 85 carried by the table 4. The table 4 is provided with a longitudinal slot and means are provided whereby the dogs 84 and 85 can be adjusted longitudinally along the slot and secured in adjusted positions.

From vthe foregoing description it will be apparent that the reversing mechanism is controlled by the table 4 as it moves longitudinally. However, thegactual shifting of the clutch collar 59 is effected by power received independently ofthe table. The table merely releases the latch 67 which serves to transmit the power for operating the clutch.

Assuming grinding to be taking place and t-he table 4 to be moving toward the right, it will be clear that continued movement will cause the dog 84 to engage the bellcrank 83 and swing it in the clockwise di,

rection. This will move the link 82 upward and will swing the lever 81 in the clockwise direction, thus moving the rod 78 downward. Downward movement of the rod 78 will cause the trip 71 to be disengaged from the` latch 68, whereupon the cam 65 will be rotated, thus connecting the high speed reversed drive/for the drum 42. When the drum 42 is reversed the s indley is reversed and also the lead screw 9. The reversed movement of the lead screw causes the carriageto be moved quickly toward the left, this movement continuing until the dog 85 engages the bell-crank 83 and moves it in the counter-clockwise direction. Then .the link 82 is moved downward and the rod 78 is moved upward, thus disengaging the trip 72 from the latch 67. The cam 65 is then rotated and connects the low speed normal drive for the drum 42. These operations are repeated indefinitely, the spindle being periodically reversed and the carriage being reciprocated in synchronismwith the spindle movements. The table movement in the grinding direction is relatively slow and the table movement in. the other direction is ielatively rapid.

It has already been pointed out that for grinding left-hand threads, grinding must take place while the carriagev is moving toward the left. It is therefore necessary for the high speed reversed drive for the spindle to be connected at the end of the table movement toward the left and for the low speed normal drive to be connected at the end of the table movement toward the right, this being the reverse of the connections during the grinding of right-hand threads. This reversal is effected by disconnecting the link 82 from the left-hand arm of the bell-crank 83 and connecting it to the right-hand arm.

In order that the movements of the spindle and of the table may be readily stopped by the operator when required, I provide an arm 86 secured to the front end of the pivot shaft 61 which carries the lever 60. A hand lever 87 is pivoted to the main frame and carries a pin 88 which extends into a slot 89 in the arln 86. The slot 8,9 is wide at its lower end so that when the lever 87- is in the position shown the arm 86 can be swung freely whenever the lever 60 is moved by the cam 65. The upper end of the slot 89 is narrow and the result is that when the lever 87 is swung in the clockwise direction,

the pin 88 entering the narrow upper end of the notch 89, moves the arm 86 and therefore the lever 60 and the clutch collar 59 to their central neutral positions. The clutch collar 59 is thus disconnected from both of the gears 51 and 58, and the drum 42 and all of the parts driven thereby remain idle.

Because of unavoidable back-lash and lost motion in the various connections, it is highly preferable that the grinding wheel be disengaged from the blank at the end of movement in the grinding direction and reengaged with the blank at the end of movement in the return direction. In order that this may be done, and in order further that the grinding wheel may be properly adjusted and fed, the wheel 28 is mounted on a carriage 90 which is movable forward and backward on guideways 91 and 92 formed on the main frame. A bracket 93 projects upward from the carriage and a plate 94 is secured to the bracket; The plate 94 carries bearings 95 and 96 in which is rotatably mounted a spindle 97 carrying the wheel 28. The plate 94 is angularly adjustable, with respect to the bracket 93, about a trans-a verse horizontal axis which preferably passes through the center of the grinding wheel. As shown, the plate 94 is provided with two arcuate slots 98 and 99 through which extend bolts 100 and 101 secured to the bracket 93. By loosening the nuts on these bolts the plate can be adjusted to position the wheel.

28 at any desired angle to conform to the angular pitch of the threads to be ground. After adplstment the plate 94, together with the spindle and the wheel, can be locked in adjusted positions by tightening the nuts on the bolts. Preferablya scale 102 is provided to show the adjustmentl of the wheel.

Securedl to the end of the spindle 97 `opposite to the wheel is a belt pulley 103 and this pulley is engaged by a belt 104 which passes over a pulley 105 at the rear of the carriage 90. The pulley 105 is mounted on a short horizontal shaft 106 which also carries a belt pulley 107. A belt 108 engages the pulley 107 and also passes around a pulley 109 on the main drive shaft 44. A tightener pulley 108a is provided for the belt 108. The belt 104 permits the wheel and the spindle to be adjusted angularly without disturbing the power connection, and the belt 108 permits the carriage 90 with the wheel to be moved forward or backward without disturbing the power connection.

When the grinding wheel is in grinding engagement with the work, the carriage 90 is in its forward position. When the table 4 is reversed and moved backward the carriage 90 with the wheel must be drawn backward in order to disengage the wheel from the work. For effecting this backward movement the following mechanism is provided. The cam 65 is provided with a lthird cam surface which engages a roller 110 at the upper end of a lever 111. This lever 111 is secured -to a transverse shaft 112 which extends through to the front of the main frame. At the front the shaft 112 carries a lever 113 to which is connected the lower end of a link 114. The link 114 extends diagonally upward and at its upper end, as shown in Fig. 13, it is connected with `one arm of a bell-crank 115 which is pivoted to the main frame at 116. The other arm of the bell-crank is forked and carries shoes fitting notches in a collar 117. The collar 117 fits a transverse shaft 118 and is held against rotative movement by means of a pin 119. The shaft 118 is rotatably and slidmain frame.

abl f mounted in bearings in the main frame an the rear end of the shaft is connected with the carriage 90. vThe collar 117 abuts against a collar 120 fixedly secured to the shaft 118. The cam 65 is so formed that the llever 111 is moved just before the direct `drive for the drum 42 isthrown into action.

The movement of the lever 111 serves to move the link 114 upward, thus rocking the bell-crank 115 in the clockwise direction and pushing the shaft 118 toward the rear. The shaft 118 carries with it the 'carriage' 90 and the grinding wheel 28, thus disenga ing-the wheel from the work. Subsequent y at the commencement of the movement of the table in the inding direction, the cam 65 permits the ever 111 to be moved to its original position. For moving the carriage and the grinding wheel forward I do not depend upon .the cam 65 but upon a weight 121 which is connected with the carriage by means of chains 122 passing over idler pulleys 123. As soon as theposition of the cam 65 permits, the carriage and the wheelv are moved forward by the weight until the collar 120 abuts agalnst the collar 117 and` until the collar 117 abuts against the Preferably the bearings at bothl sides of the collar 117 are kept free from oil so that there will be no o1l films to affect the position of the carriage. Inasmuch as the machine is intended for very accurate work, it is absolutely essential for the carriage to be restoredto exactly its original position after each backward movement.

It is ordinarily necessary for the wheel to be passed over a gage a number of times in order to complete the grinding operation and a relative feeding. must be eHected from time to time. This feeding is effected by moving the carriage 90, use preferably being made of the aforesaid shaft118. The shaft is threaded at its rear end and extends through a threaded lug 124 depending from the carriage. The shaft 118 carries a gear 125 at its front end, and this gear meshes with a pinion 126 on a short transverse horizontal shaft 127. Loosely mounted on the shaft 127 at its rear end are two gears 128 and 129. 130 on a short transverse shaft 131. This shaft also carries a gear 132 which meshes with a pinion 133 on a short transverse shaft 134. The gear 129 meshes with an idler gear 135 which in turn meshes with a gear 136 secured to the said shaft 134. Either of the gears 128 or 129 may be connected with the shaft 127 by means of a sliding key 137 which is controlled by a manually operable rod 138 slidably mounted within thel shaft 127. The shaft 134 carries'a hand wheel vns The gear 128 meshes with a gear While feeding may be effected by hand, IY

prefer to provide means whereby it can be effected automatically by power. As illustrated, the shaft 134 `carries a' ratchet wheel 140. Mounted for pivotal movement about the axis of the shaft 134 is a lever 141 carrying a pawl 142 engaging the teeth of the ratchet wheel 140. The rod 114 carries a piny 143 which engages the lever 141 and moves it whentherod vis moved upward. Thefpawl 142 turns the ratchet wheel 140 which in turn feedsxthe wheel through the gearing which has been described. When the rod 114 moves downward the lever 141 moves inthe reverse direction, either by gravity or'by a spring, and preferably an adjustable stop 144 is rovided which engages the lopposite en of the lever and limits its backward movement. Preferably a second lever 145 is frictionally connected with the ratchet Wheel 140'so as to move therewith. This lever 145 carriesv a shield 146 which extends over the ratchet wheel. As the ratchet wheel is turnedthe. shield 146 moves underthe pawl 142, thus holding it out of engagement with the wheel and stopping the feeding operation. By `properly setting the arm 145 with respect to the ratchet wheel, the feeding can be stopped at -any desired position. j

Obviously, the accuracy of the threads depends largely upon the accuracy with which the wheel is dressed, and I therefore preferably provide a wheel dressing mechanism which is united -with and which forms a permanent part of the machine. So far as certain features of my invention are concerned, the exact location of the dressing mechanism is immaterial. Preferably, however, I locate the mechanism at the rear of thewheel so that the dressing tools will act on the wheel along a horizontal plane which passes through the wheel center and which also passes through the axis of adjustment of the wheel.

As illustrated in Figs. 14 and 15, the carriage 90 has a bracket 147 which projects laterally therefrom at the rear of the wheel and which serves as a support and guideway for a slide 148. By means of bolts 149 the slide may be secured in adjusted position. The upper part of the slide 148 is in the 'form of a broad plate 150 having its periphery in the form of a circular arc, the center of which at 151 is approximately vertical beneath the edge of the wheel at the rear. At one side, as for instance at the left-hand side, the plate 150 has an arcuate groove 152 constructed about the center 151. A plate 153 rests upon the late 150 and has an arcuate tongue which ts the groove 152. It will be seen that the plate 153 may be angularly adjusted about the center 151, being guided by the walls of the groove 152 during such movement. A scale 154 is provided on the plate 150 for indicatinr the angular adjustment of the plate 153. bolt 155 projects downward from the plate 153 through a slot 156 in the plate 150. By means of this bolt the plate 153 can be secured in adjusted position. l

Formed on the top of the plate 153 is a guideway for a slide 157 which can be movedunder the control of a screw carrying a handle 158. Formed on the top of the slide 157 is a guideway for a slide 159 which can be moved under the control of a screw carrying a handle 160. The two slides 157 and 159 are movable at right angles to each other. The slide 159 carries a suitable dressing tool 161. I have shown a diamond pointed tool, but it will be understood that the invention is not so limited.

At its opposite side the plate 150 carries a plate 162 which is similar to the plate 153 and which is similarly supported and guided. The plate 150 is provided with a scale 163 for indicating the angular adjust-r l ment of the plate 162. ICarried by the plate 162 is a slide 164 controlled by a screw having a handle 165. Carried by the slide 164 is a slide 166 'controlled by a screw having a handle 167. The slides 164 and 166 are` similar respectively to tlie slides 157 and 159. The slide 166 carries a dressing tool 166l Asimilar to the tool 161.

When the dressing mechanism is to be used, the slide 148 is adjusted forward or backward in accordance with the diameter of the wheel so as to bring the center 151 a proximately vertically beneath the rear edge of the wheel. Thenthe plates 153 and 162 are angularly adjusted so as to bring the slides 159 and 166'at the proper angles to the central-plane of the wheel. Ordinarily both slides are placed at an angle of 30, this angle being read directly on the scale 154 and 163. Then one of the slides, as for instance 157, is adjusted to move the dressing tool, 161 into positionto engage the edge of the wheel. By means of the screw 160 the slide 159 is then moved forward or backward to move the dressing tool along the wheel and properly dress one side thereof. Then the other tool 166a is brought into operative relation to the wheel by means of the slide 164 and is moved forward and backward by means of the slide 166. After the wheel has been properly dressed the two slides 157 and 164 are moved backward to withdraw the tools from engagement with the wheel. Preferably the screws for the two slides carry respectively scales 168 and 169 which enable the operator to restore the slides to their former positions, when it again becomesnecessary to dress the Wheel.

It will be seen that, inasmuch as the dressing tools are at the back of the wheel and directly opposite the points of engagement between the wheel and the work, they automatically compensate for errors which would otherwise arise because of angular adjustment of the wheel.

The Atool dressing mechanism that I have shown and described does not of itself constitute a part of the present invention, it being presented in'my co ending application for wheel dressing mec anism, Serial No. 222,929, filed on even date herewith. I do, however, herein claim the novel relationship between the wheel dressing mechanism and the other parts of the grinding machine.

What I claim is:

1. The combination in a thread grinding machine, of means including a longitudinally movable headstock and spindle for holding and rotating a blank to be ground, a rotatable grinding wheel for grinding threadson the blank, a rotatable lead screw connected with theheadstock for longitudinal movement therewith, a fixed nut engaging the lead screw, gearing connecting the spindle and the lead screw, and means for driving and periodically reversing the spindle and thus reversing the lead screw and the headstock.

2. The combination in a thread grinding machine, of means including a longitudinally movable headstock and s indle for holding and rotating a blank to e ground, a rotatable grinding wheel for grinding threads on the blank, means positively connected with the spindle for moving the headstock and blank longitudinally with respect to the wheel in timed relation. yvith the blank rotation, a belt pulley on the spindle, a wide belt drum parallel with the spindle, a belt passing around the pulley and drum and permitting the pulley to move longitudinally with the spindle, and means for driving and periodically reversing the drum and thus reversing the spindle and the headstock.

3. The combination in a thread grinding machine, of means including a headstock and spindle for holding and rotating a blank to be ground, a rotatable grinding wheel for grinding threads on the blank, a transversely movable carriage on which the wheel is mounted, means positively connected with the spindle for moving the headstock and the blank longitudinally with respect to the wheel in timed relation to the blank rotation, driving means connected with the spindle, means actuated by the headstock for reversing the driving means after movement of the headstock to a predetermined extent in each direction, and means actuated by the reversing mechanism at each operation thereof for positively moving the carriage rearward to disengage the vwheel from the blank `at the end of movement in one direction and permitting moving the carriage forward -to reengage the wheel with the blank at the end of movement in the other direction. i

4. The combination in a thread grinding y machine, of means including a headstock and spindle for holdingand rotating a blank. to be ground, a rotatable grinding wheel for grinding threads on the blank,

means positively connected with the spindleV for effecting relative longitudinal movement between the blank and the wheel in timed relation to the blank rotation, automatic means for periodically reversing the-rotation \and the longitudinal movement and for causing the movement in one direction to be more rapid than in the other, and positivey automatically acting means for disengaging the wheel from the blank at the'end of the slower movement in one direction and permitting reengaging the wheel with the blank at the end of the more-rapid movement in the other direction.

5. The combination in a thread grinding machine, of means including a headstock and spindle for holding and rotating ablank to .be ground, a rotatable grinding wheel for .grinding threads on the blank, means positively connected with the spindle for moving the headstock and the blank longitudinally with respect to the wheel in timed relation to the blank rotation, means connected with the spindle for driving the spindle and the headstock relatively slowly in one direction and relatively rapidly in the other direction, and means controlled by the headstock' for reversing the driving means after movement of the headstock toa predetermined extent in each direction.

6. The combination in a thread grinding machine, of means including a headstock and spindle for holding and rotating a blank to be ground, a rotatable grinding wheel for grinding threadson theblank, means including motion reversing gearing positively connected with the spindle for eecting relative longitudinal movement in either direction between the blank and the wheel in timed relation to the blank'rotation, automatic means for periodicallyv reversing the spindle rotation and the longitudinal movement, and automatically acting means for disengaging the wheel from the blank at the end of movement in one direction and for reengaging the wheel with the blank at the end of movement in the other direction.

7. The combination in a thread grinding machine, of means including a headstock and spindle for holding and rotating a blank to 'be ground, a rotatable grinding wheel for grinding threads on the blank, means inc luding motion reversing gearing positively connected with the spindle for eecting relative longitudinal movement in either direction between the blank and the wheel 1n timed relation to the blank `rotation, automatic means for periodically reversing the spindle rotation and the longitudinal movement, and positive automatically acting means foru disengaging the vwheel from the blank at the end of the slower movement in one direction and permitting reengaging the wheel with the blank at the end of the more rapid movement in the other direction.

8. The combination in a thread grinding machine, of means including a headstock and spindle forv holding and rotating a blank Ito vbe ground, a/rotatable grinding wheel for grinding threads on the blank, means including motion reversing gearing positively connected with the spindle for effecting relative longitudinal movement in either direction between the blank and the wheel in timed relation to the blank rotation, automatic means Jfor periodically reversing the spindle rotation and the longitudinal movement, 'automatically acting means for disengaging the Wheel from the blank at the end of movement in one direction and for reengaging the wheel with the blank at theend of movement in the other direction, and means for transposing the tive longitudinalcmovement in either direction between the blank and the wheel in timed relation to the blank rotation, automatic means for periodically reversing the spindle rotation and the longitudinal move-- ment and for causing the movement in one direction to be more rapid than in the other, positive automatically acting means for disengaging the wheel from the blank at the end of the slower movement in one direction and permitting reengaging the wheel with the blank at the end of the more rapid movementvin the other direction, and means for transposing the disengaging and reengaging movements of the grinding wheel.

10. The combination in a thread grind- .ing machine, of means including a headstock and spindle for holding and rotating a blank to be ground, a rotatable grinding wheel for grinding threads on the blank, means positively connected with the spindle for effecting relativelongitudinal movement between the blank and the wheel in timed relation to the blank rotation, means for periodically reversing the spindle rotation and the longitudinal movement, automatically acting means for disengaging the wheel from the blank at the end of movement in one direction and for reengaging the wheel with the blank vat the end of.

movement in the other direction, and means for supplementally moving the carriage on which said wheel is mounted to regulate the engagement of the 'wheel with the blank.

v1l. The combination in a thread grinding machine, of means including a headstock to a predetermined extent in each direction, automaticallyacting means including a bodily movable screw; for moving the carriage on which said wheel is mounted rearward to disengage the wheel from the blank at the end of movement in one direction and for moving the carriage forward to reengage the wheel with the blank at the end of movement in the other direction,

and means for rotating the screw to sup' plementally move the carriage to regulate the engagement of the wheel with the blank.

-12. \The combination-in a thread grinding machine, of means including a headstock and spindle for holding and rotating a blank to be ground, a rotatable grinding wheel for grinding threads on the blank, a transversely movable carriage on which the wheel is mounted, means positively connected with the spindle for moving the headstock and the blank longitudinally with respect to the wheel in timed relation to the blank rotation, driving means connected with the spindle, means for reversing the driving means after movement of theheadstock to. a predetermined extent in each direction, automatically acting means for moving the carriage rearward to disengage the wheel from the blank at the end of movement in one direction and for moving the carriage forward to reen age the wheel with the blank at the end o other direction, and means for supplementally moving the carriage' to regulate the engagement .of the wheel with the blank.

movement in the 13. The combination in a thread grinding-machine, of means including a headstock and spindle for holding and rotating a blank to be ground, a rotatable grinding wheel for grinding threads on the blank, means positively connected with the spindle for effecting relative longitudinal movementbetween the blank and the wheel in timed rela- ,ing means for disengaging the wheel from the blank at the end of movement in one` direction and for reengaging the wheel with the blank at the end of movement in the other direction, and mechanism for automatically moving the carriage on which said wheel is mounted forward a supplemental distance at each reengagement with the blank to effect feeding.

14. The combination in a thread grinding machine, of means including a headstock and s indle for holding and rotating a blank to e ground, a rotatablegrinding wheel for grinding threads on the blank, a transversely movable carriage on which the wheel is mounted, means positively connected with the spindle for moving the headstock and the blank longitudinally with respect to the wheel in timed relation to the blank rotation, driving means connected with the spindle, means for reversing the driving means after movement of the headstock to a predetermined extent in each direction, automatically acting means for moving the carriage rearward to disengage the wheel from the blank at` the end of' movement in onedirection and for moving the carriage forward to reengage the wheel with the blank at the end of movement in the other direction, and mechanism for automatically moving the carriage forward a supplemental distance at each reengagement with the blank to effect feeding.

15. The combination in a thread grinding machine, of means including a headstock and spindle for holding and rotatingI a blank to be ground, a rotatable grinding wheel for grinding threads on the blank, a transversely movable carriage on which the wheel is mounted, means positively connected with the spindle for moving the headstock and the blank longitudinally with respect to the wheel in `timed relation to the blank rotation, driving means connected with the spindle, means for reversing the driving means afterm movement of the headstock to a predetermined extent in each direction, automatically acting means for moving the carriage rearward to disengage the wheel from the blank at the end of movement in one direction and for moving the carria e forward to reengage the wheel with t e blank at the end of movement in the other direction, and mechanism operated by the last said means for automatically moving the carriage forward a supplemental distance at each reengagement with the blank to effect feeding.

16. The combination in a thread grinding machine, of means including a headstock and spindle for holding and rotating a blank to .be ground, a rotatable grinding wheel for grmdmg threads on the blank, a transversely movable carriage on which the wheel 1s mounted, means positivel `connected with the-spindle for moving t e headstock and the blank longitudinally with res ect to the wheel in timed relation to the b ank rotatlon, driving means connected with the spmdle, means for reversing the driving means after movement of the headstock to a predetermined extent in each direction, automatically acting means for moving the carriage rearward to disengage the wheel from the blank at the end of movement in one direction and for moving the carriage forward to reengage the wheel with the blank at the end of movement in the other direction, mechanism for automatically moving the carriage forward a supplemental distance at each reengagement with the blank to eifect feeding, and means for stopping the feeding movement at a predetermined position.

17. The combination in a thread grinding machine, of means for holding and rotating a blank to be ground, a rotatable grinding wheel for grinding threads on the blank, means for adjusting the wheel angularly in accordance with the' pitch of the threads 18. The combination in a thread grinding machine, of means for holding and rotating a blank to be ground, a rotatable grinding wheel for grinding threads on the blank, means for adjusting the wheel angularly in accordance with the pitch of the threads about a horizontal axis passing through its center and through the axis of the blank, and a wheel dressing mechanism comprising two independent tools movable at an angle to each other and each positioned to engage the wheel along a line lying in a horizontal plane passing through the axis of the blank and the axis of adjustment of the wheel.

19. The combination in a threadgrinding machine, of means for holding and rotating a blank to be ground, a rotatable grinding wheel for grinding threads on the blank, means for adjusting the wheel angularly in accordance with the pitch of the threads about an axis passing through its center and -wheel along a line ying in a plane assing through the axis of the blankV and t e axis of adjustment of the 'Wheel and each adjustable mdependently of the other `about an\ axis perpendicular to the last said plane.

20, The combination in a .thread grinding machine; of means for'holdinga'nd rotating a blankl tobe ground', a rotatable grinding Wheel' for grinding threads on the blank, and mechanism for dressing said grinding Wheel comprisingrtwo slides angularly adjustable about. a common axis and `positioned'at opposite` sides of the central lane of the Wheel and `movable at acute ang es to the said' lane, and dressing tools carrled respective y bysaid slides.

21. Thcombination in a thread grinding inachine,` of means for holding and rotating 'a-vblank to beI'gr'ound, 'a rotatable'grindin jwheel for grinding threads on the blank, an

`mechanism for dressing said grindin Wheel comprisingtwo slides angularl ,A ad]ustable about a common axis norma ly approximately tangent to the periphery iof the wheel 'and positioned at opposite sides of the central planeof the wheel and movable at acute angles to the said plane, and dressing tools 26 carried respectively by'said slides.

In testimony whereof,v I heretoalx my signature.

ANDERS E.' LARSSON.- 

